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SCD Sound prob

Arakon - Sep 20, 2003

		Arakon		Sep 20, 2003
			friend of mine brought a scd 2 for checking today.. on some FMV games as well as in the chuck rock 2 intro, the music sounds like it's playing way too fast.. but the video is perfectly fine. only happens on games without cd audio tracks, and not on all.. but with the ones it does, it always happens. the games are flawless, the genny too (verified). it's clean inside, the lense is clean too. any ideas?

		Curtis		Sep 20, 2003
			Wow...that sounds like a technical impossibility - especially with a single speed CD drive. The only thing I can think is that the games are copies and not very good ones, but you've ruled that one out already. How much faster does the audio play?

		racketboy		Sep 20, 2003
			wow Arakon has a problem he can't fix? hehe

		Arakon		Sep 21, 2003
			they are originals. I ruled out most physical problems, so I'm gonna have to guess it's a fried chip somewhere.. there're even games that work half and half... the logo has skipping sound, the intro works flawless.

		Mask of Destiny		Sep 21, 2003
			Sounds like something funky is going on with either the PCM chip or the clock line that feeds it, but I'm pretty sure it runs off the same clock as the 68K so if that was the problem, you'd probably see problems elsewhere. I don't have the faintest idea how you would fix that.

		Alexvrb		Sep 23, 2003
			Would you see problems elsewhere? Last I checked it wasn't terribly sensitive to clockspeed changes as far as how the games run, as they have emulators that underclock the 68k for a speed gain. Maybe your Sega CD is running too fast? Also as I recall, the SNES does not react well to clock speed changes.

Mask of Destiny

Sep 23, 2003

	
	
		
		
			Originally posted by Alexvrb@Sep 23, 2003 @ 05:43 AM



 Would you see problems elsewhere? Last I checked it wasn't terribly sensitive to clockspeed changes as far as how the games run, as they have emulators that underclock the 68k for a speed gain. Maybe your Sega CD is running too fast? Also as I recall, the SNES does not react well to clock speed changes.

It depends on the game. Some of them don't do a proper handshake, so if one of the processors doesn't run at the right speed they miss each other. That's why Sega CD emus have a "Perfect Synchro" option.

		Alexvrb		Sep 23, 2003
			What if they are both slower or faster, together? Probably not. But its possible that (since its actual hardware and not an emu) one or more of his chips is not running at the proper speed, and yet it has no problem doing a handshake. I mean, that's a pretty weird problem, especially since it doesn't happen with all games, and its consistent.

Mask of Destiny

Sep 24, 2003

	
	
		
		
			Originally posted by Alexvrb@Sep 24, 2003 @ 04:03 AM



 What if they are both slower or faster, together? Probably not. But its possible that (since its actual hardware and not an emu) one or more of his chips is not running at the proper speed, and yet it has no problem doing a handshake. I mean, that's a pretty weird problem, especially since it doesn't happen with all games, and its consistent.

The Genesis 68K and the Sega CD 68K are fed by two separate crystals. They wouldn't fluctuate in speed together. The inconsistency of the problem is hard to explain. I suppose it's possible the games that are working properly are using the DAC on the YM-2612 as opposed to the PCM chip in the Sega CD, but that seems kind of silly.